The Berkeley Seismological Laboratory (BSL), formerly the
Berkeley Seismographic Station (BSS), is the oldest Organized Research Unit
(ORU) on the UC Berkeley campus.
Its mission is unique in that, in addition to research and education in
seismology and earthquake-related science, it is responsible for providing
timely information on earthquakes (particularly those that occur in northern
and central California) to the UC Berkeley constituency, the general public,
and various local and state government and private organizations. The BSL is
therefore both a research center and a facility/data resource, which sets it
apart from most other ORUs. A major component of our activities is focused
on developing and maintaining several regional observational networks,
and participating, along with other agencies,
in various aspects of the collection, analysis, archival,
and distribution of data pertaining to earthquakes, while maintaining a
vigorous research program on earthquake processes and Earth structure.
In addition, the BSL staff spends considerable time with public relations
activities,
including tours, talks to public groups, responding to public inquiries about
earthquakes, and, more recently, World-Wide-Web presence
(http://www.seismo.berkeley.edu/seismo/).

UC Berkeley installed the first seismograph in the Western Hemisphere at
Mount Hamilton (MHC) in 1887. Since then, it has played a leading role in
the operation of state-of-the-art seismic instruments and in the development
of advanced methods for seismic data analysis and interpretation. Notably, the
installation, starting in 1927, of Wood-Anderson seismographs at 4 locations
in northern California (BKS, ARC, MIN and MHC) allowed the accurate
determination
of local earthquake magnitude () from which a unique historical catalog
of regional earthquakes has been maintained to this day, providing crucial
input to earthquake probabilities studies.

Over the years, the BSS continued to keep apace of technological improvements.
The first centrally telemetered network using phone lines in an active seismic
region was installed by BSS in 1960. The BSS was the
first institution in California to
operate a 3-component ``broadband" system (1963). Notably,
the BSS played a major
role in the early characterization of earthquake
sources using ``moment tensors"
and source-time functions, and made important contributions to the early
definitions of detection/discrimination of underground nuclear tests and to
earthquake hazards work, jointly with UCB Engineering.
Starting in 1986, the BSS
acquired 4 state-of-the-art broadband instruments (STS-1), while simultaneously
developing PC-based digital telemetry, albeit with limited resources. As the
telecommunication and computer technology made rapid progress, in parallel with
broadband instrument development, paper record reading could be
completely abandoned
in favor of largely automated digital data analysis.

The current modern facilities of BSL have been progressively built over
the last 14 years, initiated by significant ``upgrade" funding from UC Berkeley
in 1991-1995. The BSL currently operates and acquires data, continuously
and in real-time, from over 60 regional observatories, housing a combination
of broadband and strong motion seismic instrumentation installed in vaults,
borehole seismic instrumentation, permanent GPS stations of the Bay Area
Regional Deformation (BARD) network, and electromagnetic
sensors. The seismic data are fed into the BSL real-time processing and
analysis
system and are used in conjunction with data from the USGS NCSN network
in the joint earthquake notification program for northern California,
started in 1996.
This program capitalizes on the complementary
capabilities of the networks operated by each institution to provide rapid
and reliable information on the location, size and other relevant source
parameters of regional earthquakes. In recent years, a major emphasis in
BSL instrumentation has been in densifying the state-of-the-art
seismic and geodetic networks, while a major on-going
emphasis in research has been the development of robust methods for quasi-real
time automatic determination of earthquake source parameters and predicted
strong ground motion, using a sparse network combining broadband and strong
motion seismic sensors, as well as permanent geodetic GPS receivers.

The backbone of the BSL operations is a regional network of
25+ digital
broadband and strong motion seismic stations,
the Berkeley Digital Seismic Network (BDSN),
with continuous telemetry to UC Berkeley.
This network provides the basic regional data
for the real-time estimation of location, size
and rupture parameters for earthquakes of
M 3 and larger in central and northern
California, within our Rapid Earthquake Data
Integration (REDI) program and is the Berkeley
contribution to the California Integrated
Seismic Network (CISN). It also provides a
fundamental database for the investigation of
three-dimensional crustal structure and its
effects on regional seismic wave propagation, which is
ultimately crucial for estimating ground shaking for
future earthquakes. Most stations
also record auxiliary temperature/pressure
channels, valuable in particular for background
noise quality control. Complementing this network
is a station ``high-resolution" network
of borehole seismic sensors located along the Hayward
Fault (HFN) and under the Bay Area
bridges, operated jointly with the
USGS/Menlo Park and linked to the Bridge Safety Project
of the California Department of Transportation (Caltrans).
The latter has facilitated the
installation of sensor packages at 15 bedrock
boreholes along 5 east-bay bridges in
collaboration with Lawrence Livermore
National Laboratory (LLNL). A major
science goal of this network is to collect high
signal-to-noise data for micro-earthquakes along
the Hayward Fault to gain insight
into the physics that govern fault rupture and its nucleation. The BSL is also
involved in the operation and maintenance of the 13 element Parkfield borehole
seismic array (HRSN), which is yielding enlightening results on quasi-periodic
behavior of micro-earthquake clusters and important new
constraints on earthquake
scaling laws and is currently playing an important role
in the characterization of
the site for the future San Andreas Fault Observatory at
Depth (SAFOD). Since April 2002,
the BSL is also involved in the operation of a permanent broadband ocean bottom
station, MOBB, in collaboration with MBARI (Monterey Bay Aquarium Research
Institute).

In addition to the seismic networks, the BSL is involved in data archival and
distribution for the permanent geodetic BARD
Network as well as the operation, maintenance, and data processing
of 22 out of its 70+ sites. Whenever possible, BARD sites are collocated with
BDSN sites in order to minimize telemetry costs. In particular, the
development of
analysis methods combining the seismic and geodetic data for the
rapid estimation of source
parameters of significant earthquakes has been one focus of BSL research.

Finally, two of the BDSN stations (PKD, SAO) also share data acquisition and telemetry with
5-component electromagnetic sensors installed with the goal of investigating
the possibility of detection of tectonic signals. In 2002-2003, an automated quality control software
was implemented to monitor the electromagnetic data.

Archival and distribution of data from these and other regional networks is
performed at the Northern California Earthquake Data Center (NCEDC), operated
at the BSL in collaboration with USGS/Menlo Park. The data reside on a mass-storage
device (current holdings TerraBytes), and are accessible ``on-line" over
the Internet (http://www.quake.geo.berkeley.edu). Among others, data from the USGS Northern
California Seismic Network (NCSN), are archived and distributed through the
NCEDC. The NCEDC also maintains, archives and distributes the ANSS/CNSS earthquake catalog.

Core University funding to our ORU has suffered from permanent budget cuts to research programs from
the State of California, and currently provides salary support for 2 field engineers, one
computer expert, 2 data analysts, 1 staff scientist and 2 administrative staff. This supports a
diminishing portion of the operations of the BDSN and provides seed funding for our
other activities. All other programs are supported through extra-mural grants primarily
from the USGS and NSF, and in the past five years, the Governor's Office of Emergency
Services (OES). We acknowledge valuable recent contributions from other sources such as Caltrans,
the CLC program and PEER, as well as our Earthquake Research Affiliates.

Chapter 3 documents the
main research contributions of the past year.
Research at the BSL spans a broad range of topics,
from the study of microseismicity
at the local scale to global deep earth structure,
and includes the use of seismological,
geodetic, and remote sensing (InSAR) techniques.

Richard Allen and his students have continued to develop a methodology for
earthquake early warning (4,12), documenting, in
particular, that, for large earthquakes, the frequency
content of radiated seismic energy within
the first few seconds of rupture scales with the final magnitude of the
event.

Bob Nadeau and collaborators continued to work on characteristically
repeating micro-earthquakes (5,8). In particular,
Nadeau has extended the
study published in 2004 to investigate if the time varying
patterns of periodic pulsing of
deep slip, extends through an additional 5 years.
The successful prediction of time periods
with increased likelihood for larger earthquakes based on his earlier
data suggest that there is significant potential in his approach to
refine time dependent earthquake forecasts, at least for the central
San Andreas Fault segment (5). Nadeau and collaborators are
also studying repeating earthquakes in other tectonic settings, such as
Taiwan (7).

Studies of data generated by the M6 2004 Parkfield earthquakes continue.
Nadeau and collaborators have been further documenting the time and space
distribution of non-volcanic tremors on the
San Andreas fault near Parkfield (6). Graduate student
Karl Kappler has been refining EM data analysis procedures (20,
37, 21). Doug Dreger and his
student Ahyi Kim have developed a kinematic model of the Parkfield earthquake
using jointly GPS and seismic data (9).

Doug Dreger and his students and collaborators have also worked on a variety of source and
structure topics including the development of a promising method to
identify seismic events with a strong isotropic component, very relevant to
the recent nuclear test in North Korea (10), new earthquake ground
motion simulations using the recently developed USGS SF06 velocity model
(11), the determination of structure in the Santa Clara
Valley using both teleseisms and microearthquake data (24), and
evaluation of methodologies to constrain attenuation models in northern
California (17).

Geodetic studies include work by Roland Bürgmann and his students and
post-docs on the surface deformation in the San Francisco Bay Area
using InSAR data
(22) and on the motion of the Indian plate (18), as
well as work by Nicolas Houlié and collaborators on the
deformation of the Etna
volcano, using GPS (19).
In a collaborative effort involving three BSL faculty members (Dreger,
Bürgmann and Romanowicz), separate tools developed by each of them were combined by graduate student Junkee Rhie
to obtain a slip model for the great M9 2004 Sumatra earthquake, based on
teleseismic and near field geodetic data (23).

Other regional studies include continuation by Bob Uhrhammer
of the study of Bay Area historical seismicity
(15) and, in particular, scanning of old
seismograms with the help of undergraduates (16); the study by Peggy Hellweg of an unusual sequence of earthquakes
near Orinda, CA (14); and the development of a methodology to
reduce long period ocean noise at the broadband ocean bottom station MOBB(24).

On the topic of relation of oceanography and seismology, Romanowicz and her
student Junkee Rhie have continued their study of the relation of ocean
storms to the earth's long period noise known as "hum", and followed a
particular sequence of storms across the Pacific (25), showing how the generation
of the hum involves a three stage process (ocean waves, infragravity waves,
seismic waves).

Deep earth structure studies start in the upper mantle, with work by
graduate student Mei Xue with
Richard Allen on a regional tomographic model beneath northwestern US,
tracking
the fate of the Juan de Fuca plate down to 400 km (27),
while post-doc Federica Marone, working with Barbara Romanowicz, has
developed a tomographic model of S velocity and anisotropy beneath the entire
North
American continent, documenting the presence of two layers of anisotropy
beneath the stable continent, one in the lithosphere and one in the asthenosphere (29). Federica has also been working, with
collaborators at Northwestern Univ., on a similar model for the Mediterranean
region (32). Also on the regional scale, graduate student
Ahyi Kim, working with post-doc Mark
Panning and Barbara Romanowicz, has developed a regional upper mantle 3D
model for southeast Asia (30). This model is the first step
towards developing a higher resolution model of this region using more
sophisticated tools for 3D wave propagation.

As in previous years, Romanowicz and her group have continued their work on
refining tomographic models of mantle structure at the global scale
(33,31) and have started to obtain results from a new
approach, combining seismic and mineral physics constraints to map
lateral variations of temperature and composition in the upper
mantle (26). Also, graduate student Ved Lekic has started
constructing a new global 3D model of attenuation in the upper mantle,
using the spectral element method to compute synthetic seismograms in an
elastic model (28). With post-doc Aimin Cao,
Romanowicz also continues work on core structure, one example of
which is given in
this report, documenting the possible presence of short wavelength topography
on the inner core boundary (34).

Finally, combining expertise in seismology and geodynamics, a
study of the constraints on the structure of Jupiter's satellite Europa
that could be obtained with seismic data has given rise to two
publications (35), while Ved Lekic, working with Michael
Manga, has been investigating tidal excitation of free oscillations on
Saturn's moon Enceladus (36).

Highlights in 2005-06 include the BSL's participation in the commemoration
activities of the 1906 earthquake's centennial anniversary (see Chapter 46).
These activities included a joint SSA/EERI/DRC conference which was
held in San Francisco in April 2006. The BSL, and specifically
Dr Peggy Hellweg, were heavily involved in its organization.
The BSL also helped develop many exhibits, classes, and a series of
public lectures on the UC Berkeley Campus, which were held between October 2005
and April 2006. Richard Allen and Barbara Romanowicz taught a Freshman
Seminar on the subject of the 1906 earthquake and earthquake preparedness,
which resulted in an informational movie, put together by the students, and
targeted at incoming Berkeley freshmen. This movie is available through several
websites on Campus, in particular:
http://seismo.berkeley.edu/~rallen/BEAR

Another new activity began in February 2006, with funding from NSF through
the IRIS/GSN program (Global Seismic Network). It is a collaborative project
with Tom VanZandt of Metrozet on the design and testing of new electronics
for the STS-1 very broadband seismometer which occupies
several hundred sites around the world, and in particular
10 of the Berkeley sites. The manufacturer of this sensor
of unsurpassed quality has discontinued its production,
but no equivalent new instrument of
any design is available. Meanwhile the STS-1s,
many of which have been around
for 15-20 years, are deteriorating with age. In the Spring of 2006,
significant effort was deployed at BSL to set up a testbed at the Byerly
Vault to test successive iterations of new electronics developed by
Metrozet.

As in the previous year, BSL's infrastructure development
efforts have centered around several major projects:

operation and enhancement of the joint earthquake notification system
with USGS/Menlo Park.

the continuing development of the California Integrated Seismic Network

participation, at various levels, in three components
of the national Earthscope program: the deployment in
northern California of the BigFoot component of
USArray, archival of borehole strainmeter data in the framework of the
Plate Boundary Observatory (PBO), and the preparation for archival of the
data from the San Andreas Fault Observatory at Depth (SAFOD).

development of borehole networks at Parkfield and along the Hayward Fault

operation and further enhancements of the BARD network of continuous GPS

operation of the Northern California Earthquake Data Center

The main goal of the CISN (see Chapter 39) is to ensure
a more uniform system for earthquake
monitoring and reporting in California. The highest priority, from the point of
view of emergency responders in California, is to improve the robustness of
statewide real-time notification and to achieve a uniform interface across
the State to the California OES and other emergency responders.
This represents a major
challenge, as the CISN started as a heterogeneous collection of networks with
disparate instrumentation, software systems and culture. Much effort has gone over the past few years to develop coordinated software between southern and
northern California and in northern California, between Berkeley and
USGS/Menlo Park. These two institutions are joined together in the
Northern California Earthquake Management Center(NCEMC). Until now,
earthquake processing responsibilities were divided into two components.
Responsibility for running the association, location and duration
magnitude modules has resided with Menlo Park, while local and moment
magnitude, and finite-fault modules run in Berkeley. Redundancy is
built into the system by operating two complete systems at all times,
the second one as a "hot" backup. Recognizing potential problems
associated with the separation of critical system elements across
the San Francisco Bay, an effort was launched in 2001 to redesign the
Northern California operations. In the new system, which is currently in
advanced test mode, two complete systems, which provide processing from
detection to location and
computation of ground motion parameters and Shakemaps, will operate
one in Berkeley and one in Menlo Park. Its implementation is awaiting
the retirement of the CUSP real-time earthquake timing system in Menlo
Park (see chapter 44).
In the past year, CISN funds were also used to complete new broadband
stations at Alder Springs, CA (GASB), and at the Marconi Conference Center
near Point Reyes (MCCM). FEMA funds made available following the San
Simeon earthquake of 2003 are being
combined with CISN funds, to purchase equipment for 7 additional new stations
that will fill gaps in the present
distribution of broadband stations in northern California. This past year the
equipment has been ordered and the sites identified among
currently operating temporary northern California sites of
the Earthscope/USArray program.
BSL staff continue to spend considerable efforts in organizational
activities for CISN,
notably by participating in the CISN Project Management Group
(Neuhauser and Hellweg), which
includes weekly 2 hour phone conferences, and the Standards Committee
(Neuhauser-chair, Hellweg, Lombard), which strives to define and coordinate
software development tasks. Romanowicz and Hellweg serve on the CISN Steering
Committee. Doug Neuhauser has also been serving on the CISN Steering Committee
in the transition period following Lind Gee's departure in summer
2005. The CISN also represents
California as a designated region of ANSS (Advanced National Seismic System)
and the BSL is actively involved in planning activities for the ANSS.

The BSL concluded an agreement in June 2004 with IRIS to contribute 19
stations of the BDSN to USArray, while the experiment is deployed in
California. This includes 17 existing stations and the two new sites
mentioned above: GASB and MCCM. In the past year, BSL has continued to
acquire telemetered data from these and other northern
California USArray stations and to pay particular attention to the maintenance
of those permanent sites which are part of USArray.

The BSL has completed the relocation of the critical operations of data
acquisition, processing, archiving and data distribution to 2195 Hearst
(``SRB-1"), a recently completed building on Oxford Tract, which was
constructed to current seismic codes, with special attention to
post-earthquakes operability of the campus computer facility. The
computer center contains state-of-the-art
seismic bracing, UPS power and air conditioning with generator back-up
and extensive security and equipment monitoring. In the past year, BSL
has finished moving all of its
data acquisition, real-time earthquake processing computers, and data
archive and distribution computers to the new facility, including
telemetry equipment.

The Parkfield borehole network (HRSN, see
chapter 41) undertook an effort to upgrade power modules in
early 2005. This has now been completed and has effectively eliminated
data drop outs and gaps that had plagued the network during the winter
months. The HRSN
continues to play a key role in support of the Earthscope SAFOD (San
Andreas Fault Observatory at Depth) drilling project, by providing low
noise waveforms for events in the vicinity of the target drilling zone.
A procedure
is underway to refine an automated similar event detection method based
on cross-correlation and pattern scanning of the continuous HRSN data,
to assist
researchers working on repeating micro-earthquakes as well as those working
on the target events in the SAFOD drilling zone.

In the past year, infrastructure development for the Northern Hayward
Fault Network (NHFN, see chapter 40) has progressed notably.
The coverage on the west side of the Bay has
been augmented with the installation of the "Mini-PBO" station MHDL (Marin
Headlands), which comprises borehole seismometers and a continuous GPS
receiver. It is now part of the NHFN and of the BARD 42
network. Caltrans has
provided funding and support for instrumentation of 3 land sites for
the NHFN. Station VALB (Vallejo, CA) is operational, whereas PETB
(Petaluma River Bridge) is instrumented and awaiting completion of
telemetry infrastructure. The third hole has been drilled at St.
Mary's College (SMCB) and is nearing completion.
On-going network maintenance involves regular inspection of the
collected
seismic waveform data and spectra for nearby seismic events, and
for noise samples, in order to assure that the instruments operate
at maximum performance to
capture the source spectrum of micro-earthquakes down to negative magnitudes.

The last year has been a transition period for the BARD continuous
GPS (C-GPS) network, with the departure of Mark Murray and arrival
of Nicolas Houlié. Also, the landscape has been changing in northern
California with the construction of the Plate Boundary Observatory (PBO) of
Earthscope, which is installing many new C-GPS stations. We are working
with PBO to transfer several of our stations to PBO, those that are
either not accessible by continuous telemetry or
collocated with broadband seismic stations. We are also refocusing
BARD on
real-time continuous data acquisition at high sampling rates for
earthquake hazards applications, responding to a growing interest
of our own researchers and of the community. Data from the BARD
stations have been traditionally
acquired at 15 or 30 s sampling rates, but, for these applications, 1 s or
higher sampling rates are needed. Conversion to these higher rates is limited
by the telemetry capabilities and nature of receivers at each individual
station. We started collecting 1 Hz data at 2 stations in 2003. In the last
year,
we progressively upgraded nine additional stations to continuous 1
Hz telemetry.
These data are made publicly available at the NCEDC, while we develop
methods to combine them with seismic data in our real-time earthquake
notification system. We have recently acquired 5 new receivers (Ashtech Z)
which will enable us to upgrade several of the sites collocated with BDSN
stations.

The NCEDC (see Chapter 43), continues archival and
on-line distribution of data from expanding BDSN, NHFN, HRSN, BARD,
Mini-PBO, and other networks and data collections in northern California and
Nevada, including telemetered continuous data from USArray
stations in northern California and vicinity. We are continuing to
receive data from the SAFOD pilot hole and main hole, and data from
15 SCSN (southern California) broadband sites as part of the CISN
robust ``backbone".
Previously, only event data were archived from the 1000+ components
of the Northern California Seismic Network (NCSN) operated by USGS/Menlo Park.
As a major accomplishement in the past year, we have developed the
necessary software and procedures and are now archiving
continuous NCSN seismograms at NCEDC. We have developed software and
are retroactively working our way to
transfer older data from tapes to complete the on-line collection.
Having easy access to these continuous data is important, in
particular, for scientists working on non-volcanic tremors. It is
also of
interest to global seismologists working on body waves from large
teleseisms.
The change from event archiving to continuous archiving has significantly
increased the amount of data archived (from 35GB/year to 1750 GB/year).
This was accomplished with no additional NCEDC staff, and was made possible by
our work to automate the data delivery and archival process, and by
the significant
decrease in the cost of RAID disk systems.

Finally, with seed funding from the USGS to Prof. Richard Allen, we
have started work on the establishment
and testing of a prototype earthquake early warning system.

This past year has seen many changes in BSL personnel. Following
Eleanor Blair's
retirement, Kristen Jensen joined BSL as our new Manager in February 2006.
Kristen previously worked as senior analyst in the office of the VCR. We are
very fortunate to have her. Jenny Pehl left BSL in July 2006 to follow her
husband to a new job in Las Vegas. Nicolas Houlié was hired as a post-doc
in February 2006 to take responsibility for our continuous GPS program.

Four graduate students associated with BSL completed their PhD's in
the past year: Aimin Cao, Junkee Rhie, David Dolenc and Ingrid Johannson.
Ingrid joined the USGS/Menlo Park on a Mendenhall Post-doc, David is in
Minnesota (Univ. of Minnesota in Duluth), while Aimin and Junkee are staying
on as post-doc's at BSL. Mark Panning, who had stayed as post-doc at BSL after
completing his PhD in Fall 2004, left
for Princeton in July 2006, where he has a post-doctoral
fellowship.

New arrivals have continued through the summer and early Fall of 2006.
Kevin Mayeda
transferred from LLNL to join BSL research staff in July, while
Cyndy Bresloff has been helping with
routine processing and data quality control since mid-August.
Tina Barber-Riggins joined the business office in
September.
Alexei Kireev and Mario Aranha
joined the programming team in September and October, respectively.
They will assist Doug Neuhauser
with tasks related to
the CISN, the Early Warning Project and the NCEDC.

This year has also been marked by very sad news: Professor Bruce Bolt, who was
Director of the Seismographic Stations from 1963 to 1989, passed away
after a brief illness on July 21, 2005, just a few months before the start of
the celebrations of the 1906 San Francisco earthquake centennial. A memorial,
attended by over 500 people,
was held for him at the Faculty Club on July 29, 2005.
We include in this report a copy of the obituary
(draft version as of 10/17/06) which we have been putting together
for UC Berkeley.

I wish to thank our technical and administrative staff, scientists and
students for their efforts throughout the year and their contributions
to this Annual Report. Individual contributions to activities and report
preparation are mentioned in the corresponding sections, except for the
Appendix section, prepared by Kate Conner and Kristen Jensen.

I also wish to specially thank the individuals who have regularly contributed
to the smooth operation of the BSL facilities:
Rich Clymer, Doug Dreger, John Friday, Jarrett Gardner,
Peggy Hellweg, Nicolas Houlié, Bill Karavas, Rick Lellinger,
Pete Lombard, Rick McKenzie, Mark Murray, Bob Nadeau, Doug Neuhauser,
Charley Paffenbarger, Bob Uhrhammer, and Stephane Zuzlewski, and in the
administrative office, Kristen Jensen, Kate Conner, Jenny Pehl and Yolanda
Andrade. I particularly wish to thank Doug Dreger for serving
as Associate Director of
the BSL, Peggy Hellweg for taking on responsibilities for CISN and data
analysis coordination, Doug Neuhauser for his efforts to build the
Earthscope related archival system, and Bill Karavas for organizing
an effective test bed for the refurbishment of the STS-1 electronics.